Amplitude dependence of image quality in atomically-resolved bimodal atomic microscopy

In bimodal FM-AFM, two flexural modes are excited simultaneously. The total vertical oscillation deflection range of the tip is the sum of the peak-to-peak amplitudes of both flexural modes (sum amplitude). We show atomically resolved images of KBr(100) in ambient conditions in bimodal AFM that display a strong correlation between image quality and sum amplitude. When the sum amplitude becomes larger than about 200 pm, the signal-to-noise ratio (SNR) is drastically decreased. We propose this is caused by the temporary presence of one or more water layers in the tip-sample gap. These water layers screen the short range interaction and must be displaced with each oscillation cycle. Further decreasing the sum amplitude, however, causes a decrease in SNR. Therefore, the highest SNR in ambient conditions is achieved when the sum amplitude is slightly less than the thickness of the primary hydration layer.Comment: 3000 words, 3 Figures, 3 supplimentary figure

音叉型水晶振動子を力センサーとして用いた非接触原子間顕微鏡の開発

13301甲第4399号博士(理学)金沢大学博士論文要旨Abstrac

音叉型水晶振動子を力センサーとして用いた非接触原子間顕微鏡の開発

13301甲第4399号博士(理学)金沢大学博士論文本文Ful

大気環境における潮解性物質表面の原子単位局所溶解制御

金沢大学理工研究域数物科学系本研究では、低湿度(RH20%)から高湿度(RH90%)までの広い湿度範囲で動作する大気型周波数変調原子間力顕微鏡を開発した。開発装置を用いて湿度制御した大気中でKBr単結晶の(001)劈開面を観察し、微量の水が吸着した際の固体-水界面特性を解析した。RH30%-45%の低湿度では、原子フラットなKBrテラス上は1分子厚さの水膜で一様に覆われ、KBrの溶解析出はほとんど生じなかった。RH50%-60%の加湿環境では、KBr上に厚さ約3nmの水膜が形成された。3nmの水膜で覆われたKBr結晶表面に、AFM探針を用いて精密制御した力を印加すると、原子単位の結晶溶解を誘起できることを明らかにした。We developed frequency modulation atomic force microscopy which operable in the wide humidity range even in dry(RH20%) to humid(RH90%) air conditions. Using custom-build instruments, the solid-water interracial property when a small amount of water adsorbed on KBr(001) plane was analyzed with the high resolution observation.In the dry air conditions as RH30%-45%, KBr(001) cleavage plane was uniformly covered by water with the thickness of 1 or 2 molecules, and dissolution/deposition of KBr was almost stopped. In slightly humidified air as RH50%-60%, thin water film with the thickness of 3nm was formed on KBr. When the KBr crystal is covered by nano-meter water film, atomically dissolution of crystal surface can be mechanically induced by applying the precisely controlled force using the FM-AFM technique.研究課題/領域番号:17K14115, 研究期間(年度):2017-04-01 – 2019-03-3

Two-Step On-Surface Synthesis of One-Dimensional Nanographene Chains

Controllable fabrication of low-dimensional graphene structures is a matter of scientific and technological interest. To date, significant efforts have been devoted to the fabrication of nanographene chains as well as nanographenes and graphene nanoribbons. Here, we present the on-surface synthesis of one-dimensional (1D) nanographene chains composed of hexa-peri-hexabenzocoronene (HBC) which is a common type of nanographene. Using dibromo-substituted hexaphenylbenzene (Br2-HPB) as a precursor, the 1D HBC nanographene chains are achieved through two reaction steps, namely polymerization and cyclodehydrogenation, on a Au(111) surface, which have been investigated by low-temperature scanning tunneling microscopy. The Br2-HPB molecules deposited on Au(111) are formed into a chiral selective self-assembled layer, and the following thermal annealing at 200–300 °C induces debromination and sequential polymerization of Br2-HPB, leading to the formation of long 1D HPB chains. In particular, we find that the same length 1D HPB chains are selectively ordered in a side-by-side arrangement. Finally, by annealing at 400 °C, HBC planar nanographenes are achieved through the cyclodehydrogenation process of HPB within the long 1D chains. The maximum length of the obtained 1D HBC nanographene chains reached is about 30 nm

Resonance frequency-retuned quartz tuning fork as a force sensor for noncontact atomic force microscopy

Based on a two-prong type quartz tuning fork, a force sensor with a high Q factor, which we call a retuned fork sensor, was developed for non-contact atomic force microscopy (nc-AFM) with atomic resolution. By cutting a small notch and attaching an AFM tip to one prong, its resonance frequency can be retuned to that of the other intact prong. In balancing the two prongs in this manner, a high Q factor (>50 000 in ultrahigh vacuum) is obtained for the sensor. An atomic resolution image of the Si(111)-7 × 7 surface was demonstrated using an nc-AFM with the sensor. The dependence of the Q factor on resonance frequency of the sensor and the long-range force between tip and sample were measured and analyzed in view of the various dissipation channels. Dissipation in the signal detection circuit turned out to be mainly limited by the total Q factor of the nc-AFM system

Multiple Administrations of 64Cu-ATSM as a Novel Therapeutic Option for Glioblastoma: a Translational Study Using Mice with Xenografts

Glioblastoma is the most aggressive malignant brain tumor in humans and is difficult to cure using currenttreatment options. Hypoxic regions are frequently found in glioblastoma, and increased levels of hypoxia areassociated with poor clinical outcomes of glioblastoma patients. Hypoxia plays important roles in the progressionand recurrence of glioblastoma because of drug delivery deficiencies and induction of hypoxia-inducible factor-1αin tumor cells, which lead to poor prognosis. We focused on a promising hypoxia-targeted internal radiotherapyagent, 64Cu-diacetyl-bis (N4-methylthiosemicarbazone) (64Cu-ATSM), to address the need for additional treatmentfor glioblastoma. This compound can target the overreduced state under hypoxic conditions within tumors.Clinical positron emission tomography studies using radiolabeled Cu-ATSM have shown that Cu-ATSMaccumulates in glioblastoma and its uptake is associated with high hypoxia-inducible factor-1α expression. Toevaluate the therapeutic potential of this agent for glioblastoma, we examined the efficacy of 64Cu-ATSM in micebearing U87MG glioblastoma tumors. Administration of single dosage (18.5, 37, 74, 111, and 148 MBq) andmultiple dosages (37 MBq × 4) of 64Cu-ATSM was investigated. Single administration of 64Cu-ATSM in high-dosegroups dose-dependently inhibited tumor growth and prolonged survival, with slight and reverse signs of adverseevents. Multiple dosages of 64Cu-ATSM remarkably inhibited tumor growth and prolonged survival. By splitting thedose of 64Cu-ATSM, no adverse effects were observed. Our findings indicate that multiple administrations of64Cu-ATSM have effective antitumor effects in glioblastoma without side effects, indicating its potential fortreating this fatal disease